1. Technical Field
The present invention relates to a dimmer and a projector.
2. Related Art
As a projector in which a light blocking member is used for adjustment of a lighting device, there is known a projector in which a pair of tabular light blocking members that can be opened and closed by pivoting are symmetrically arranged across an illumination optical axis between a pair of lens arrays in the lighting device to adjust a light blocking amount of illumination light. There is also known a projector in which a block-like light blocking body is used as such a light blocking member and a dent like a cutout is provided in the light blocking body to adjust a change in a light blocking amount. However, when such a block-like light blocking body having the cutout is used as the light blocking member, it is necessary to form a complicated curved surface at an end of the light blocking body in order to set the change in the light blocking amount to a desired change. In this case, a space for the light blocking body is also necessary. However, a space around the pair of lens arrays is limited. Therefore, it may be difficult to set the block-like light blocking body.
Therefore, JP-A-2010-217651 proposes a configuration in which a light blocking section includes a first light blocking member and a second light blocking member. Since the first light blocking member includes a cutout section, it is possible to make a change in a light blocking amount relatively gentle. The second light blocking member changes a light blocking region for light corresponding to the cutout section to block all or a part of a light beam corresponding to the cutout section during full closing of the first light blocking member.
JP-A-2011-118322 discloses a projector including an illumination optical system including a light source, light blocking sections that can partially block a light beam from the light source, and a driving mechanism that causes the light blocking sections to operate and a light modulating device illuminated by illumination light from the illumination optical system. The light blocking sections are driven by the driving mechanism to pivot around predetermined pivot axes to change the size of a blocking region. The light blocking sections include distal end side ends corresponding to a boundary between the blocking region and a non-blocking region during pivoting. The distal end side ends include a first region and a second region located further on the light source side than the first region during the pivoting of the light blocking sections. The first region is divided into plural regions at the distal end side ends. The second region is located between the divided regions of the first region. With this configuration, it is possible to provide a projector that can sufficiently reduce an illumination light amount in a maximum blocked state while making a change in a light blocking amount relatively gentle.
The pair of light blocking members described in JP-A-2011-418322 open and close in the center in an up down direction (or left right direction) with respect to an optical axis of a light beam emitted from a lighting device to adjust a light amount of the emitted light beam. The pair of light blocking members are set to have a fixed space (separation distance) between ends on the optical axis side of the pair of light blocking members in a state in which the light amount is the smallest (a state in which the light blocking members close).
However, when light blocking is performed by causing the pair of tabular light blocking members to open and close, it is likely that a change in a light blocking amount is not gentle. Therefore, color unevenness tends to occur. Further, fluctuation in position control for the light blocking members increases. As a result, there is a limit in a light blocking amount (a closing amount) by the light blocking members in order to suppress the color unevenness to permissible color unevenness. Therefore, it is difficult to increase a contrast ratio.
When an extinction ratio (a ratio of blocking of a light beam) by a dimmer is improved, it is necessary to reduce the separation distance between the ends of the light blocking members in the state in which a light amount is the smallest (the state in which the light blocking members are close).
When the light blocking sections are arranged on a downstream side of an optical path where the light beam from the light source is changed to a partial light beam using a lens array in which small lenses are arranged in a matrix shape as described in JP-A-2011-118322, if a region between the pair of light blocking sections in a maximum light blocking state does not include the center of the small lenses of the lens array and is a boundary of the small lenses or a peripheral region of the boundary, the intensity of the light beam in the boundary and the peripheral region of the boundary is low compared with the center. Therefore, even if the separation distance is large, a relatively high extinction ratio can be set. However, if the region between the pair of light blocking sections in the maximum light blocking state includes the center of the small lenses of the lens array where the intensity of the light beam is high, it is difficult to obtain a sufficient extinction ratio unless the separation distance is set particularly small. However, if the separation distance is set small or removed, the light blocking members interfere with each other because of fluctuation in machining accuracy of the light blocking members, assembly accuracy of the dimmer, and the like.
Therefore, there is a demand for a dimmer and a projector that can maintain a separation distance between ends of light blocking members to improve an extinction ratio and can suppress color unevenness to realize a high contrast ratio.